A tropical storm is brewing in the Atlantic Ocean. It’s causing rain and thunderstorms over the Caribbean, and it will soon be a tropical depression — the beginning of a hurricane. By the time Hurricane Mitch leaves the Central America, more than 11,000 people will be dead and as many as 18,000 more will be missing. (Activity adapted from Mapping Our World at http://edcommunity.esri.com/MOW.)

No matter where we are on Earth, we can observe changes in vegetation. Some changes are drastic, such as going from dormant to full growth during a temperate winter.

Vegetative growth is dependent on both surface temperature (which influences soil temperature) and precipitation (which influences soil moisture). Together these environmental variables help determine the beginning, duration, and end of the growing season; the latter marked by leaf senescence, when leaves of deciduous trees die and turn colors.